1. This experiment.

2. The appropriate sections of your textbook.

1. A 0.1 M solution of an acid, HA, in water is prepared. It is found that at equilibrium, the solution has a pH of 4.2. Calculate the value of K_a for the acid, HA.
2. At what value of pH will the concentrations of the acid from 1), HA, and its conjugate base (A-) be the same?
3. 2.00 mL of a solution of the acid from problem 1) of unknown concentration is titrated with 0.1040 M NaOH to a phenolphthalein endpoint. Exactly 0.94 mL of NaOH solution is required. What is the concentration of the acid solution?
4. Another 2.00 mL of the HA solution from 3) is treated with 0.47 mL of 0.1040 M NaOH, exactly half the amount required to neutralize the acid in the solution. What is the pH of the resulting solution?
5. Set up a table showing how the value of the ratio, R, varies with pH for the acid, HA, from problem 1). Plot pH versus log R. Can you use this plot to determine K_a for the acid? How? (HINT: consider CONVENIENT R values between 0.01 and 100.)